A micro-grid system is a small electrical grid having a plurality of electricity generating devices that may be configured to service a localized power load. Among other components, the micro-grid system may include a plurality of electrical generators (gensets) running in parallel that service the load. When the plurality of gensets are the primary sources supplying power to the load, these gensets are generally run in an n+1 (or greater than n+1) arrangement. This means that at least one additional genset than the number of gensets needed to meet the load demand is run to satisfy that demand. By virtue of running the one or more extra gensets, the micro-grid system is able to maintain voltage and frequency of power within specification with minimum to no disruptions to the power load when block loads are added to the micro-grid system.
Furthermore, in some paralleled genset operations running in the n+1 arrangement, the gensets may be running at only about a sixty percent (60%) load factor. Load factor may be defined as an average load divided by a peak load in a specified amount of time. One reason for operating the gensets at a lower load factor could be that at high load factors, the response of the micro-grid system when the gensets encounter block loads may not be sufficient. However, it is well known that fuel efficiency of a genset increases when the genset is run closer to a full load capacity, that is, the fuel efficiency increases at higher load factors. Thus, running the gensets at only a sixty percent (60%) load factor may not be very fuel efficient.
Additionally, the engines of the gensets in some micro-grid systems may have associated therewith a turbo compounding system that may increase fuel efficiency at least somewhat by converting heat and airflow energy from engine exhaust gasses of the gensets into electrical, mechanical or other type energy to provide additional power. However, turbo compounding increases fuel efficiency the greatest when the engine of the gensets is running close to full load. Therefore, with the gensets running at only about sixty percent (60%) load factor, turbo compounding may not be very advantageous.
U.S. Pat. No. 7,047,743 discloses a system of using electric turbo compounding with a genset to supply power to a grid. Specifically, the patent teaches a turbo-generator, the electric output of which is combined with the electric output of an engine powered generator to increase total power output for a given size and to improve fuel efficiency. The combined power is then delivered to a transmission line. Although the above patent teaches using an electric turbo compounding system with a genset to increase total power output, the patent does not teach increasing the load factor of the genset itself. As discussed above, without increasing the load factor of the genset, the electric turbo compounding system does not provide any significant fuel savings. Furthermore, it appears that the engine powered generator in the '743 patent is operated at the conventional n+1 configuration.
It would accordingly be beneficial if a mechanism for improving the operating efficiency and fuel efficiency of the gensets in a micro-grid system could be developed. It would additionally be beneficial if such a mechanism could operate the gensets at a higher load factor while providing sufficient response in transient conditions.